Time to cut the racetrack. Remember that this piece will be your tabletop, so make sure your cuts are smooth.

I used a very fine jigsaw blade with 20 teeth-per-inch (TPI).

To start your cut, simply drill a hole (on the line) with a drill bit just a tad larger than your jigsaw blade (1/4" is probably plenty). I suggest drilling the holes just inside your line (on the felt insert part). That will allow the drill hole to be covered up when you pad and felt the insert. If you drill your hole outside the line, your hole will forever be visible on the racetrack. Better to have your imperfections hidden I always say!  

 

 

 

Here is the tabletop with the racetrack & felt insert cut. My clamps wouldn't reach that far inside the board, so I simply laid some extra wood underneath it to keep it steady and level while I was making the cuts. Remember that you don't want the wood to fall out while you're sawing.

Try your best to make nice even cuts, because the racetrack wood will be exposed, and any imperfections on the racetrak will be viewable. 
 
A view of all the pieces together after the cutting is complete. 
 
 Close up of rail, racetrack, and felt insert.